The researchers at National Institute of Standards and Technology (NIST) and Georgia Tech have discovered that flower-shaped defects in graphene effect its electrical and mechanical properties.
Flower-like defects in graphene can occur during the fabrication process. The NIST team captured images of one of the defects (figures a and c) using a scanning tunneling microscope
The team has discovered a total of seven possible defects, one of which was observed before. The relation between mechanical strength and electrical conductivity of graphene and its structure has already been established.
According to a Fellow at NIST, the defects in graphene are caused by the movement of carbon molecules during the manufacture of graphene from silicon carbide under high temperature and high vacuum conditions. Of all the possible rearrangements of atoms, the easiest requiring minimum energy is the formation of five or member rings from six-member rings. The NIST team has discovered that this re-arrangement creates a new defect in the honey comb lattice of graphene.
Eric Cockayne, NIST researcher, explained that when graphene is subjected to extreme heat, some parts of the lattice come loose and start rotating. When the temperature is brought down, these loose sections re-attach with the lattice but in a haphazard manner. The flower-like defect patterns that are formed by this mechanism increase the strength of graphene. Cockayne added that further experiments could lead to establishing a relation between the appearance of the defect and the growth variations. The NIST team’s model of the atomic structure of graphene reveals the flower like defects which possess unique mechanical and chemical properties.
Source: http://www.nist.gov/